Shuttle transfer with sine wave time/velocity acceleration

ABSTRACT

A stacker crane elevator has drive mechanism for exending a twopart load bearing shuttle from centered position on the elevator into a selected pigeonhole of an automated warehouse and vice versa. The drive mechanism accelerates and decelerates the shuttle in a sine curve time/velocity ratio by means of two crank-like drive pins mounted on a rotative head member and interposed one between each of two parallel drive faces. Orbital movement of the crank pins through circular arcs of 180* rotative movement of the head member produces acceleration of the shuttle from zero velocity through maximum and back to zero in a sine wave curve which tends to equalize acceleration throughout shuttle travel and thus to minimize displacement of a load on the shuttle.

[ 51 Oct. 16, 1973 1 SHUTTLE TRANSFER WITH SINE WAVE TIME/VELOCITYACCELERATION [75] Inventor: Taylor D. Whltenack, Jr., Bonita, PrimaryExaminer-Manuel AmPnakaS m Assistant Examiner-Wesley S. Ratliff, Jr.Attorney-George F. Pearson [73] Asstgnee: Rohr Industries, Inc., ChulaVista,

Calif.

[57] ABSTRACT A stacker crane elevator has drive mechanism for ex- [22]Filed: Apr. 12, 1972 [21] Appl. No.: 243,228 tendmg a two-part loadbearing shuttle from centered position on the elevator into a selectedpigeonhole of [52] 11.8. 74/29, 214/16.4 A an automated warehouse andvice versa. The drive [51] Int. Fl6h 19/04 mechanism accelerates anddecelerates the shuttle in a [58] Field ofSearch.......................... sine curve time/velocity ratio by meansof two crank- 214/l6.4 A, 16.1 C like drive pins mounted on a rotativehead member v and interposed one between each of two parallel drive [56]References Cited faces. Orbital movement of the crank pins through cir-NI D A S PATENTS cular arcs of 180 rotative movement of the head3,429,195 2/1969 74/29 member pmduces accelerati the shuttle fmm3,371,804

zero velocity through maximum and back to zero in a 4/1968 Chasar....2l4/16.4 A 214/16.1 C

sine wave curve which tends to equalize acceleration throughout shuttletravel and thus to minimize displacement of a load on the shuttle.

2,951,599 9/1960 Bogar.....

12/1969 A1stedt...........................

FOREIGN PATENTS OR APPLICATIONS 920,316 11/1954 Germany 74/29 10 Claims,4 Drawing Figures PATENTED 08] 161975 SHEU 2 BF 2 SHUTTLE TRANSFER WITHSINE WAVE TIME/VELOCITY ACCELERATION BACKGROUND OF THE INVENTION In anautomated warehouse where loads are transferred from conveyors tostacker cranes and thence to selected pigeonholes in racks providedalong aisles in which the stacker cranes operate, and vice versa, speedin all phases of the operation tends to minimize costs and maximize theutility of the installation. An important factor in the attainment ofspeed in the operation is the provision of a high speed shuttle on theusual elevator of the stacker crane which will quickly transfer a loadbetween the elevator and a selected pigeonhole.

With conventional shuttle drive means, using a drive motor operatingthrough gears or chains to transmit the driving force from the motor tothe shuttle, and a brake or reverse drive mechanism to arrest shuttlemotion at the terminal end of each shuttle movement, high accelerationand deceleration forces may be generated, tending to shift a pallet onthe suttle and a load on its pallet. Many stacker cranes with high speedshuttles now use two-speed motors in an attempt to minimize suchpositioning errors, but even then displacement errors of inch arenormal, increasing to k inch in the case of a heavy load and lightbrake. In a prior development of mine, I produced a shuttle drivemechanism using crank pins and chains to produce a modified sine curveacceleration and deceleration of shuttle movement, but in that mechanismthe sine curve ratio existed only during the initial and terminalportions of shuttle movement so that the acceleration forces were stillhigher than desired.

PURPOSE OF THE INVENTION A primary objective of the present invention isto provide drive mechanism for a high speed shuttle for a warehousestacker crane which will alternately accelerate and decelerate theshuttle on a sine wave time/- velocity curve throughout the duration ofeach shuttle movement.

Another objective of the invention is to drive a loaded shuttle betweensubstantially centered position on a stacker crane elevator platform,and extended position into a pigeonhole, and vice versa, in a minimumtime interval and with low, and relatively constant, acceleration forcesthroughout such time interval to thereby minimize shifting of a loadcarried by the shuttle.

The invention also provides a high speed shuttle drive mechanism with afixed dwell point at each limit of shuttle movement, which facilitatesstopping the shuttle in an exact, predetermined position at each suchlimit of shuttle movement.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objectives andadvantages of the invention will be apparent from the followingdescription and the accompanying drawings, wherein:

FIG. 1 is a perspective view of the base, or platform mounted portion ofa shuttle drive mechanism embodying the invention as it appears whenmounted on the elevator platform of a stacker crane.

FIG. 2 is a perspective view showing the under side of the drive blockor slider of the entire mechanism shown in FIG. 4, portions of the sliderods upon which the drive block is mounted being broken away.

FIG. 3 is a diagrammatic view in the nature of a side elevational viewof the shuttle drive mechanism, the intermediate and top shuttle membersbeing shown retracted in broken lines, and extended toward the right insolid lines, intermediate, direction reversing pinions being omitted,some changes being present in the rack and drive gears for the sake ofsimplicity.

FIG. 4 is a perspective view of the shuttle and its drive mechanism withthe shuttle extended toward the right, portions being broken away.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to the drawings indetail, a usual elevator A, see FIG. 3, of a stacker crane of a typeused in automated warehouses comprises two side frame members 11 and 10.A pair of guide roller support members 12 and 13 of steel angle materialare secured transversely across the elevator frame members 10 and II,and two pluralities of guide rollers 14 and 15 are mounted in aligned,axially parallel rows along the outer sides of these roller supportmembers to provide rolling support for an intermediate shuttle member17, see FIG. 4, to be described in detail later herein.

An upwardly facing toothed rack 18 is secured to an angle member 18mounted parallel to the roller supports 12 and 13, transversely acrossthe frame members 10 and 11. The rack 18 is positioned to drive a geartrain 19, see FIG. 4, carried by the intermediate shuttle 17, and inturn drives a load supporting shuttle 20 in a manner also to bedescribed later herein.

A second gear train 21 comprises a pair of drive gears 21a and 21b ofequal diameter with an intermediate idler pinion 21c of smaller diametertherebetween. The gears 21b and 21c are journaled on stub shafts 22b,and 22c, respectively mounted on a plate 23 secured to the elevatorframe.

The gear 21a is secured to a shaft 22a which extends through the plate23 and also through the roller support member 12, and an angle plate 24is secured to the elevator frame as best shown in FIG. 1. A pinion 25 isfixedly secured to the other end of this shaft 22a from the gear 21a,the pinion 25 being in mesh with an idler pinion 27, which in turn is inmesh with a drive gear 28. The idler pinion 27 and drive gear 28 arejournaled on short shafts 29 and 30, respectively, see FIG. I, mountedto extend between the angle member 24 and a plate 31 secured to saidangle member. A pinion 32, see FIGS. 2 and 3, is also secured to thegear shaft 30, and is in mesh with a drive rack 33, see FIGS. 2 and 4,which is part of a slider 34 mounted for slidable movement along a pairof parallel guide rods 37 and 38 rigidly mounted on the elevator frame.

The slider 34, as best shown in FIG. 2, comprises an angle member 39 towhich the drive rack 33 is secured, and a plate portion 40 secured atright angles to an upright portion of the angle member 39. A pair ofslide bearings 41 and 42, preferably of the well known ball bearingtype, are secured in axially parallel relation to the upper side of theplate portion 40, and three guide blocks 43, 44, and 45 are secured tothe lower side of the plate portion 40. The guide blocks 43 and 45arespaced equally from the center guide block 44 to provide therebetweentwo pairs of parallel drive faces 47 and 48 of equal width throughouttheir respective lengths with the exception of their open ends, whichare flared by cutting comer portions from the blocks as at 49 for apurpose which will be apparent later herein.

The slider 34 is driven between selected positions along the guide rods37 and 38 by a motor driven, rotatively mounted head member 50, seeFIGS. 3 and 4, mounted on a sub-frame 51, see FIG. 4, secured to theelevator frame. The head member 50 is secured centrally thereof to apower driven shaft 52, which is reversibly driven in selected incrementsof 180 in either direction from a selected center position by anelectric motor 53, see FIG. 4, driving through a conventional reductiongear transmission mechanism 54, also mounted on the sub-frame 51.

A pair of drive pins 57 and 58, which may be conventional ball bearingsmounted on studs, are provided one on each end of the head member 50,axially parallel to, and at equal radial distances from the axis of theshaft 52. These drive pins are of a diameter to enter between the pairsof drive faces 47 and 48 with slight clearance therefrom, and are spacedapart by the same distance as the pairs of drive faces 47 and 48. Thecentered position of the head member 50 is with the pins 57 and 58 inthe entrance ends between their respective pairs of drive faces 47 and48 with the shuttles 17 and 20 in their centered position on theelevator as shown in broken lines in FIG. 3.

The intermediate shuttle 17, see FIGS. 3 and 4, comprises a horizontalplate portion 59, see FIG. 4, with a thickened central bottom rib 60 anda central top groove 61 extending in the direction of shuttle movement,the groove providing operating clearance for a rack 62 mounted on theunder side of the top shuttle member 20. A pair of I'I-section members63 and 64, see FIG. 4, are provided one along the under side of eachside edge of the plate portion 59, and the rollers 14 and 15 on theangle members 12 and 13 are fitted for rolling, supporting movementwithin the inwardly open channels of these members.

A downwardly facing rack 65, see FIGS. 3 and 4, is secured to the underside of the plate portion 59 on the near side of the rib 60 as viewed inFIG. 4 to mesh with the drive gears 21a and 21b of the gear train 21described previously herein. The idler pinion 210 between the drivegears 21a and 21b, being of smaller diameter, clears the rack 65. Thus,a 180 clockwise rotative movement of the head member 50 from its normal,centered position, see FIG. 3, by means of the pin 58 riding in theguideway 47, moves the slider 34 with its drive rack 33 from its brokenline position of FIG. 3 to its solid line position of the same figure,which is also the position shown in FIG. 4. During this slider movementthe drive rack 33, through the pinion 32, see FIGS. 2 and 4, drive gear28, pinions 25 and 27, shaft 22a and gears 21a and 21b, drive theintermediate shuttle member 17 from its centered position on theelevator to its extended position of FIGS. 3 and 4. In the simplifieddiagram of FIG. 3, the drive rack 33 is shown as positioned below thepinion 32, and the gear 28 in mesh with the gear 210. From the gear 21a,however, the mechanism of FIG. 3 operates similarly to that of FIG. 4.

An opening 67, see FIG. 4, is provided through the central rib 60 of theplate 59 medially of the length of the groove 61, and the gear train 19,comprising the three gears 19a, 19c, and 19e, with their smaller,intermediate idler pinions 19b and 19d interposed therebetween, arejournaled on short shafts extending transversely across this opening 67,with the gears 19a, 19c, and 19e aligned to mesh with the fixed baserack 18,

and also with the rack 62 of the top or load bearing shuttle 20.

The latter shuttle comprises a plate portion 68 with a pair of side bars69 and 70 secured one along each side edge thereof. A row of alignedrollers, not shown, are journaled on mounting studs 71, see FIG. 4,along the inner side of each of the side bars 69 and 70, and ride withslight clearance in the outer grooves of the H- section side members 63and 64 of the intermediate shuttle 17. These rollers support the topshuttle 20 for free relative movement along a path parallel to that ofthe intermediate shuttle 17.

Various safety features are provided in the illustrative embodiment ofthe invention, such as shuttle limit switches 73, see FIGS. 1 and 4, asupersonic sensor 74 which sounds out" a pigeonhole to insure that it isnot already occupied before operating the shuttle drive mechanism, and aphoto cell 75, one of which is provided on each side of the elevator toinsure that no part of the shuttle or its load is projecting beyond theplatform before movement of the stacker crane is initiated. Thesedevices, however, are not features of the present invention, and thedetails thereof are, therefore, omitted.

OPERATION The operation of the illustrative form of the invention isbest visualized by reference to the diagram of FIG. 3 which forsimplicity, omits much of the supporting structure, including theshuttle supporting rollers, and also shows the drive rack 33 as mountedbelow the pinion 32, and the gear 28 in mesh directly with the gear 21a,omitting the intermediate pinions.

Assume that initially the head member 50 is in its illustrated positionof FIG. 3, but reversed counterclockwise l so that the drive pin 58 ison the left. In such reversed position of the head member, the driverack 33, the intermediate shuttle 17, and the top shuttle 20 are all intheir retracted, broken line positions of the same figure.

Assume next that the head member 50 is rotatively driven clockwise toachieve end-for-end reversal of the head member during which reversalthe drive pin 58, which was initially at the left hand end of the headmember, has now swung up and over along the broken line circle 77 ofFIG. 3, riding in the left hand guideway 47, and moving the slider 34 toits right hand, olid line position of FIG. 3. During this movement ofthe slider with its drive rack 33, the drive gears 21a and 21b have beenrotatively driven clockwise by the gear 28 to extend the intermediateshuttle 17, by means of its rack 65, to its right hand solid lineposition of FIGS. 3 and 4 During this extending movement of theintermediate shuttle 17, the gears 19a, 19c, and 19e, carried by theintermediate shuttle 17 and in mesh with both the fixed rack 18 and therack 62 of the top huttle 20, extend the top shuttle member 20 relativeto the intermediate shuttle 17 to its right hand solid line position ofFIGS. 3 and 4, which carries it and a load 78, see FIG. 3, supportedthereon, into a pigeonhole, not shown, with which it is aligned.

Reverse or counterclockwise rotative movement of the head member 50through an arc of 180 from its solid line position of FIGS. 3 and 4returns the shuttle members 17 and 20 to their centered, broken linepositions of FIG. 3, while a further 180 rotative movement,

not shown, of the head member 50 in the same counterclockwise directionwill extend the shuttles 17 and 20 toward the left in the same manner asdescribed previously herein for their extension toward the right.

Assuming that the speed of rotative movement of the head member 50 isconstant throughout each 180 of its movement, the rack and pinion drivemechanisms and the shuttles 17 and 20 will, in accordance with wellknown formulae, accelerate during the first 90 of rotative movement ofthe head member 50, and will decelerate during the second 90 of suchmovement, in a time/velocity sine curve, so that acceleration anddeceleration of the slider 34 and the shuttles 17 and 20 driven therebywill be substantially uniform throughout each 180 of head membermovement. Also, since the drive pins 57 and 58 move substantiallytangent to the faces of the guideways 47 and 48 which they contact ateach end of each such l80of head member rotation, there is thus providedat least a momentary dwell at each end of shuttle travel whichfacilitates an exact positioning of the shuttles 17 and 20 at each endof their travel. The clipped corners 49 of the blocks 43, 44, and 45 atthe entrance to each guideway act to guide the pins 57 and 58 into theirrespective guideways.

The invention provides a simple and positive shuttle drive mechanism,with smooth, sine curveacceleration and deceleration, wherein high speedcan be achieved with minimized acceleration forces, and wherein exactpositioning of the shuttle at each end of shuttle travel is easilyachieved.

Having thus described my invention, what I claim as new and useful anddesire to secure by US. letters Patent is:

l. A shuttle transfer for the elevator platform of a stacker cranecomprising,

an intermediate shuttle mounted on the elevator platform for guidedmovement along a path extending transversely of the platform,

a load bearing shuttle mounted for guided movement along a path parallelto that of the intermediate shuttle,

primary drive means to alternately accelerate and decelerate the shuttleon a sine wave time/velocity curve throughout the duration of eachshuttle movement, said primary drive means acting between the elevatorplatform and the intermediate shuttle and comprising at least one pairof parallel drive faces mounted for guided movement along a pathperpendicularly intersecting both drive faces 'of each pair thereof, thedrive faces of each pair thereof spaced apart to receive a crank-likedrive pin therebetween,

a head member mounted for controlled rotative movement back and forthabout an axis through an arc of 180 from a selected centered position,

at least one crank-like drive pin mounted on the head member at aselected radial distance from the axis of head member rotation andinterposed between one pair ofsaid drive faces, a radius from the axisof head member rotation to each crank pin being perpendicular to itsrespective pair of drive faces with the head member in its selected,centered position,

means operatively interconnecting the drive faces to the intermediateshuttle to move the intermediate shuttle with said sine wavetime/velocity acceleration from centered position on the elevatorplatform along its path of movement in a direction determined by that ofthe drive faces upon each 180 rotation of the head member, and

drive means responsive to movement of the intermediate shuttle andoperatively connected to the load bearing shuttle to move the latterfrom centered position on the intermediate shuttle along its path ofmovement relative to, in the same direction as, and at a speedproportional to, the intermediate shuttle upon each movement of theintermediate shuttle along its path of movement.

2. A shuttle transfer as claimed in claim 1 wherein the primary drivemeans accelerates the intermediate shuttle at a substantially uniformrate during the first and decelerates the intermediate shuttle at asubstantially uniform rate during the second 90, of each rotativemovement of the head member.

3. A shuttle transfer as claimed in claim 1 wherein the elevatorplatform is provided with relatively fixed, transversely extendingsupport means, and the intermediate shuttle is supported in guidedrelation on said support means for travel back and forth along its pathfrom a position wholly overlying the platform to a position extending ina selected direction laterally therebeyond.

4. A shuttle transfer as claimed in claim 1 wherein at least one supportmember extends transversely of the elevator platform, a plurality ofrollers are mounted in operative relation between each support memberand the intermediate shuttle to provide rolling, guiding support for theintermediate shuttle along its path, the drive means responsive tomovement of the intermediate shuttle comprises a first rack fixedlymounted to the elevator platform and parallel to said at least onesupport member, a second rack facing, spaced from, and parallel to thefirst rack and carried by the load bearing shuttle, and at least onegear, journaled on the intermediate shuttle and in mesh with both ofsaid racks.

5. A shuttle transfer as claimed in claim 4 wherein said at least onegear comprises a gear train consisting of a plurality of gears of equalsize aligned in a direction parallel to the paths of movement of theshuttle members, adjacent gears of said train spaced apart andoperatively interconnected by pinions of smaller diameter than saidgears, all of such pinions being clear of both of the racks.

6. A shuttle transfer as claimed in claim 1 wherein the parallel drivefaces are mounted on a slider, which is guided for selective back andforth movement along the path defined therefor in claim 1, a first rackis actuated by the slider, a second rack is mounted on the intermediateshuttle, and gearing in mesh with both racks transmits movement of theslider to move the intermediate shuttle in a selected direction alongits path.

7. A shuttle transfer for the elevator platform of a stacker cranecomprising,

an intermediate shuttle mounted on the elevator platform for guidedmovement along a path extending transversely of the platform,

a load bearing shuttle mounted on the intermediate shuttle for guidedmovement along a path parallel to that of the intermediate shuttle,

primary drive means to alternately accelerate and decelerate the shuttleon a sine wave time/velocity curve throughout the duration of eachshuttle movement, said primary drive means acting between the elevatorplatform and the intermediate shuttle and comprising two pairs of drivefaces mounted parallel to each other for guided movement along a pathperpendicularly intersecting all of said drive faces, the drive faces ofeach pair thereof spaced apart to receive a crank-like drive pintherebetween,

head member mounted for rotative movement about an axis through an arcof 180, selectively in either direction from a known centered position,pair of crank-like drive pins mounted on the head member at equal radialdistances from, and on opposite sides of, the axis of rotation of thehead member, each drive pin being interposed between a pair of saiddrive faces, each drive pin being located adjacent an end of itsrespective pair of drive faces and the radii from the axis of headmember rotation to the drive pins being perpendicular to the drive faceswith the head member in its centered position, means operativelyinterconnecting the drive faces to the intermediate shuttle to move theintermediate shuttle with said sine wave time/velocity acceleration fromcentered position on the elevator platform along its path of movement ina direction determined by that of the drive faces upon each 180 rotationof the head member, and drive means responsive to movement of theintermediate shuttle operatively connected to the load bearing shuttleand moving the latter relative to the same direction as, and at a speedproportional to, the intermediate shuttle upon each movement of theintermediate shuttle along its path of movement.

8. A shuttle transfer as claimed in claim 7 wherein the primary drivemeans comprises a slider mounted for guided, slidable movement along afixed guide track, a plurality of blocks are secured to the slider, saidblocks having straight sides spaced apart in parallel relation,adjacent, facing sides of adjacent ones of said blocks comprising saiddrive faces.

9. A shuttle transfer as claimed in claim 8 wherein the meansoperatively interconnecting the drive faces to the intermediate shuttlecomprises a first rack mounted on the slider parallel to the guidetrack, a pinion in mesh with the first rack is journaled on the elevatorplatform, a second rack is mounted on the intermediate shuttle, andgearing in mesh with both racks transmits movement of the first rack tothe second rack.

10. A shuttle transfer as claimed in claim 7 wherein the end portions ofeach pair of drive faces adjacent which the drive pins are located withthe head member in its centered position are flared to guide a drive pintherebetween when entering a guideway upon selected rotative movementsof the head member.

1. A shuttle transfer for the elevator platform of a stacker cranecomprising, an intermediate shuttle mounted on the elevator platform forguided movement along a path extending transversely of the platform, aload bearing shuttle mounted for guided movement along a path parallelto that of the intermediate shuttle, primary drive means to alternatelyaccelerate and decelerate the shuttle on a sine wave time/velocity curvethroughout the duration of each shuttle movement, said primary drivemeans acting between the elevator platform and the intermediate shuttleand comprising at least one pair of parallel drive faces mounted forguided movement along a path perpendicularly intersecting both drivefaces of each pair thereof, the drive faces of each pair thereof spacedapart to receive a crank-like drive pin therebetween, a head membermounted for controlled rotative movement back and forth about an axisthrough an arc of 180* from a selected centered position, at least onecrank-like drive pin mounted on the head member at a selected radialdistance from the axis of head member rotation and interposed betweenone pair of said drive faces, a radius from the axis of head memberrotation to each crank pin being perpendicular to its respective pair ofdrive faces with the head member in its selected, centered position,means operatively interconnecting the drive faces to the intermediateshuttle to move the intermediate shuttle with said sine wavetime/velocity acceleration from centered position on the elevatorplatform along its path of movement in a direction determined by that ofthe drive faces upon each 180* rotation of the head member, and drivemeans responsive to movement of the intermediate shuttle and operativelyconnected to the load bearing shuttle to move the latter from centeredposition on the intermediate shuttle along its path of movement relativeto, in the same direction as, and at a speed proportional to, theintermediate shuttle upon each movement of the intermediate shuttlealong its path of movement.
 2. A shuttle transfer as claimed in claim 1wherein the primary drive means accelerates the intermediate shuttle ata substantially uniform rate during the first 90* and decelerates theintermediate shuttle at a substantially uniform rate during the second90*, of each 180* rotative movement of the head member.
 3. A shuttletransfer as claimed in claim 1 wherein the elevator platform is providedwith relatively fixed, transversely extending support means, and theintermediate shuttle is supported in guided relation on said supportmeans for travel back and forth along its path from a position whollyoverlying the platform to a position extending in a selected directionlaterally therebeyond.
 4. A shuttle transfer as claimed in claim 1wherein at least one support member extends transversely of the elevatorplatform, a plurality of rollers are mounted in operative relationbetween each support member and the intermediate shuttle to providerolling, guiding support for the intermediate shuttle along its path,the drive means responsiVe to movement of the intermediate shuttlecomprises a first rack fixedly mounted to the elevator platform andparallel to said at least one support member, a second rack facing,spaced from, and parallel to the first rack and carried by the loadbearing shuttle, and at least one gear, journaled on the intermediateshuttle and in mesh with both of said racks.
 5. A shuttle transfer asclaimed in claim 4 wherein said at least one gear comprises a gear trainconsisting of a plurality of gears of equal size aligned in a directionparallel to the paths of movement of the shuttle members, adjacent gearsof said train spaced apart and operatively interconnected by pinions ofsmaller diameter than said gears, all of such pinions being clear ofboth of the racks.
 6. A shuttle transfer as claimed in claim 1 whereinthe parallel drive faces are mounted on a slider, which is guided forselective back and forth movement along the path defined therefor inclaim 1, a first rack is actuated by the slider, a second rack ismounted on the intermediate shuttle, and gearing in mesh with both rackstransmits movement of the slider to move the intermediate shuttle in aselected direction along its path.
 7. A shuttle transfer for theelevator platform of a stacker crane comprising, an intermediate shuttlemounted on the elevator platform for guided movement along a pathextending transversely of the platform, a load bearing shuttle mountedon the intermediate shuttle for guided movement along a path parallel tothat of the intermediate shuttle, primary drive means to alternatelyaccelerate and decelerate the shuttle on a sine wave time/velocity curvethroughout the duration of each shuttle movement, said primary drivemeans acting between the elevator platform and the intermediate shuttleand comprising two pairs of drive faces mounted parallel to each otherfor guided movement along a path perpendicularly intersecting all ofsaid drive faces, the drive faces of each pair thereof spaced apart toreceive a crank-like drive pin therebetween, a head member mounted forrotative movement about an axis through an arc of 180*, selectively ineither direction from a known centered position, a pair of crank-likedrive pins mounted on the head member at equal radial distances from,and on opposite sides of, the axis of rotation of the head member, eachdrive pin being interposed between a pair of said drive faces, eachdrive pin being located adjacent an end of its respective pair of drivefaces and the radii from the axis of head member rotation to the drivepins being perpendicular to the drive faces with the head member in itscentered position, means operatively interconnecting the drive faces tothe intermediate shuttle to move the intermediate shuttle with said sinewave time/velocity acceleration from centered position on the elevatorplatform along its path of movement in a direction determined by that ofthe drive faces upon each 180* rotation of the head member, and drivemeans responsive to movement of the intermediate shuttle operativelyconnected to the load bearing shuttle and moving the latter relative tothe same direction as, and at a speed proportional to, the intermediateshuttle upon each movement of the intermediate shuttle along its path ofmovement.
 8. A shuttle transfer as claimed in claim 7 wherein theprimary drive means comprises a slider mounted for guided, slidablemovement along a fixed guide track, a plurality of blocks are secured tothe slider, said blocks having straight sides spaced apart in parallelrelation, adjacent, facing sides of adjacent ones of said blockscomprising said drive faces.
 9. A shuttle transfer as claimed in claim 8wherein the means operatively interconnecting the drive faces to theintermediate shuttle comprises a first rack mounted on the sliderparallel to the guide track, a pinion in mesh with the first rack isjournaled on the elevator platform, a second rack is mounted on theintermedIate shuttle, and gearing in mesh with both racks transmitsmovement of the first rack to the second rack.
 10. A shuttle transfer asclaimed in claim 7 wherein the end portions of each pair of drive facesadjacent which the drive pins are located with the head member in itscentered position are flared to guide a drive pin therebetween whenentering a guideway upon selected rotative movements of the head member.